Timer does n't work with the form

Question

Hi, I have one class form and draw shape class. in fact I need to make the ball move around when i click Button or mouse. I design it but when i run it with the timer give me error message that the Object reference not set to an instance of an object as the photo shows.

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.IO;




namespace DRAWINGSHAPES
{
    public partial class ShapeDrawing : Form
    {
        //variables declaration
        private DrawShapesClass shapeobject;
       
        private int SizeofShape;
        private int XColOfShape;
        private int YRowOfShape;
        private float xSpeed_;
        private float ySpeed_;
        private string txtHex;
        private string shapeselected;


        private Bitmap previewbitmap;
        private Color colorselected;


        private bool DrawButtonClicked;




        public ShapeDrawing()
        {
            InitializeComponent();


            //call the "MouseClickDrawShape" method to get the mouse position and draw the shape on it 
            DrawShapesPicturebox.MouseClick += new System.Windows.Forms.MouseEventHandler(MouseClickDrawShape);


            //initialize the picture box for preview 
            previewbitmap = new Bitmap(PreviewPicturebox.Width, PreviewPicturebox.Height); 
        }


        private void DrawShapes()
        {
            //get the selected shape and store the value in the variable "shapeselected"
            if (CircleRadioButton.Checked == true)
            {
               
               
                shapeselected = "circle";
               
           
            }


            else if (SquareRadioButton.Checked == true)
            { shapeselected = "square"; }


            else if (TriangleRadioButton.Checked == true)
            { shapeselected = "triangle"; }


            //get the selected color and store the value in the variable "colorselected"
            if (RedRadioButton.Checked == true)
            { colorselected = ColorTranslator.FromHtml("#FF0000"); } //hexadecimal value for Red color


            else if (GreenRadioButton.Checked == true)
            { colorselected = ColorTranslator.FromHtml("#00FF00"); } //hexadecimal value for Green color


            else if (BlueRadioButton.Checked == true)
            { colorselected = ColorTranslator.FromHtml("#0000FF"); } //hexadecimal value for Blue color


            //check whether the drawbutton is clicked or not; if yes, then execute the method for getting the random position for the shape
            if (DrawButtonClicked == true)
            {
                DrawButtonClicked = false;
                Random randompos = new Random();


                //the random no. to get must not be smaller than the width of the picturebox
                XColOfShape = randompos.Next(DrawShapesPicturebox.Width);


                //the random no. to get must not be smaller than the height of the picturebox 
                YRowOfShape = randompos.Next(DrawShapesPicturebox.Height);


                xSpeed_ = randompos.Next(DrawShapesPicturebox.Width);
                ySpeed_ = randompos.Next(DrawShapesPicturebox.Height);
            }


            // use CreateGraphics() function for drawing the shapes in to the "DrawShapesPicturebox"
            Graphics shapegraphics = DrawShapesPicturebox.CreateGraphics();


            if (CircleRadioButton.Checked == true)
            {




                shapeselected = "circle";
                Random rand = new Random();
                shapeobject = new DrawShapesClass(DrawShapesPicturebox.DisplayRectangle, rand, 30, Color.AntiqueWhite);


            }
             
           
            shapeobject = new DrawShapesClass(XColOfShape  , YRowOfShape   , xSpeed_, ySpeed_, SizeofShape, shapeselected, colorselected);
            shapeobject.Draw(shapegraphics);
            DrawShapesPicturebox.Image = previewbitmap; 


            //use FromImage()function for saving and retrieving the image of the "DrawShapesPicturebox"; this will save to the bitmap variable or memory
            Graphics bitmapgraphics = Graphics.FromImage(previewbitmap);
            shapeobject.Draw(bitmapgraphics); 
            PreviewPicturebox.Image = previewbitmap; 
        }




        private void MouseClickDrawShape(object sender, MouseEventArgs e)
        {
            //if (CircleRadioButton.Checked == true)
            //{
            //    //shapeselected = "circle";
       
            //    // XColOfShape = e.X  ; //for "Column" mouse cursor position
            //    // YRowOfShape = e.Y  ; //for "Row" mouse cursor position
               
                 
            //}
            //else if (SquareRadioButton.Checked == true)
            //{
            //    shapeselected = "square";
            //     XColOfShape = e.X ; //for "Column" mouse cursor position
            //     YRowOfShape = e.Y ; //for "Row" mouse cursor position
            //     DrawShapes();
            //}
            //else   
            //{
               
            //    XColOfShape = e.X  ; //for "Column" mouse cursor position
            //    YRowOfShape = e.Y   ; //for "Row" mouse cursor position
            //    DrawShapes();   
            //}


             
           
           


           
        }


        private void ColorpaletteButton_Click(object sender, EventArgs e)
        {
            if (colorDialog1.ShowDialog() == DialogResult.OK)
            {
                // Store the color as a hex number
                string HexColor = string.Format("0x{0:X8}", colorDialog1.Color.ToArgb());


                // Strip the unnecessary characters at the end of the hex number
                txtHex = "#" + HexColor.Substring(HexColor.Length - 6, 6);


                colorselected = ColorTranslator.FromHtml(txtHex);


                //initialize the Color Radio buttons to false
                RedRadioButton.Checked = false;
                GreenRadioButton.Checked = false;
                BlueRadioButton.Checked = false;


            }
        }


        private void DrawButton_Click(object sender, EventArgs e)
        {
            DrawButtonClicked = true;
            DrawShapes();
        }


     
        private void SizetrackBar_Scroll(object sender, EventArgs e)
        {
            SizeofShape = SizetrackBar.Value;      //size of the shape


        }


        private void RefreshMenuOption_Click(object sender, EventArgs e)
        {
            //refresh the graphics or bitmap memory of the pictureboxes 
            DrawShapesPicturebox.Refresh();


            PreviewPicturebox.Image = null; 
            PreviewPicturebox.Invalidate(); //refresh() function cannot clear the bitmap memory


            previewbitmap = new Bitmap(PreviewPicturebox.Width, PreviewPicturebox.Height); //inialize the preview picturebox
        }


        private void DrawMenuOption_Click(object sender, EventArgs e)
        {
            DrawButtonClicked = true;
            DrawShapes();
        }


        private void ExitMenuOption_Click(object sender, EventArgs e)
        {
            this.Close();
        }


        private void DrawShapesPicturebox_Click(object sender, EventArgs e)
        {


        }


        private void timer1_Tick(object sender, EventArgs e)
        {
           
              //  shapeselected = "circle";
                shapeobject.Move(DrawShapesPicturebox.DisplayRectangle);
                DrawShapesPicturebox.Refresh();
           
        }


       
    }
}



using System;
using System.Drawing;


namespace DRAWINGSHAPES
{
    class DrawShapesClass
    {
        private float xcol;
        private float  yrow;
        private float dxcol;
        private float dyrow;
        private int shapediameter_;
        private string shapetype;
        //private Brush brushtype; <- this is used for Fill Method
      private Brush brushtype; //<- this is used for drawing line






        public DrawShapesClass(float colparam, float rowparam,float dx, float dy, int diameterparam, string shapeparam, Color colorparam)
        {
                xcol = colparam;
                yrow = rowparam;
            this.dxcol = dx;
            this.dyrow = dy;
                shapetype = shapeparam;
                shapediameter_ = diameterparam;
                //brushtype = new SolidBrush(colorparam);  //for FILL method
                brushtype = new SolidBrush (colorparam); //for drawing lines
        }


        public void Draw(Graphics graphics)
        {
            switch (shapetype)
            {
                case "circle":


                    //graphics.FillEllipse(brushtype, xcol, yrow, shapediameter, shapediameter); //for solidbrush function
                    graphics.FillEllipse(brushtype, xcol -30, yrow-15, shapediameter_, shapediameter_); //for drawing line


                    break;


                case "square":
                    //graphics.FillRectangle(brushtype, xcol, yrow, shapediameter, shapediameter); //for solidbrush function
                    graphics.FillRectangle(brushtype, xcol -30, yrow-15, shapediameter_, shapediameter_); //for drawing line
                    break;


                case "triangle":
                    {
                        //graphics.FillPolygon(brushtype, new Point[] //for solidbrush function and DrawPolygon function is for drawing lines 
                        graphics.FillPolygon(brushtype, new Point[] { new Point((int)xcol, (int)yrow), new Point((int)xcol - shapediameter_, (int)yrow + shapediameter_), new Point((int)xcol + shapediameter_, (int)yrow + shapediameter_) });
                    }
                      break;
                    }
        }


        public DrawShapesClass(Rectangle bounds, Random rand, int shapeDiameter, Color color)
        {
            xcol = rand.Next(0, bounds.Width - shapediameter_);
            yrow = rand.Next(0, bounds.Height - shapediameter_);


            dxcol = Convert.ToSingle(0.5 + 1.5 * rand.NextDouble());
            if (rand.Next(2) == 1)
            {
                {
                    dxcol = -dxcol;
                }
            }
            dyrow = Convert.ToSingle(0.5 + 1.5 * rand.NextDouble());
            if (rand.Next(2) == 1)
            {
                {
                    dyrow = -dyrow;
                }
            }
            shapediameter_ = shapeDiameter;
            brushtype = new SolidBrush(color);
        }
        public void Move(Rectangle bounds)
        {
            Move();
          Bounce(bounds);
        }
        private void Move()
        {
            xcol += dxcol;
            yrow += dyrow;
        }
        private void Bounce(Rectangle bounds)
        {
            if (xcol <= 0)
            {
                dxcol = Math.Abs(dxcol);
                xcol = bounds.Left;
            }
            else if (xcol + shapediameter_ >= bounds.Width)
            {
                dxcol = -Math.Abs(dxcol);
                xcol = bounds.Right - shapediameter_;
            }
            if (yrow <= 0)
            {
                dyrow = Math.Abs(dyrow);
                yrow = bounds.Top;
            }
            else if (yrow + shapediameter_ >= bounds.Height)
            {
                dyrow = -Math.Abs(dyrow);
                yrow = bounds.Bottom - shapediameter_;
            }
        }
        public float X
        {
            get
            {
                return xcol;
            }
            set
            {
                xcol = value;
            }
        }


        public float Y
        {
            get
            {
                return yrow;
            }
            set
            {
                yrow = value;
            }
        }


        public Point Position // create the 
        {
            get
            {
                // retrive and read 
                int x = Convert.ToInt32(xcol);
                int y = Convert.ToInt32(yrow);
                return new Point(x, y); // plan 
            }
            set
            {
                xcol = value.X;
                yrow = value.Y;
            }
        }




    }
}